1. Field of the Invention
The present invention relates generally to cutting machines such as bandsaw machines, hacksawing machines, circular sawing machines and abrasive cutting machines and, more particularly, pertains to a method and apparatus for controlling cutting machines.
2. Description of the Prior Art
The prior art concerning the present invention will be described, by way of example, in relation to what is called a horizontal bandsaw machine, although the present invention is applicable to a variety of cutting machines such as hacksawing machines, circular sawing machines and abrasive cutting machines.
As is well known, horizontal bandsaw machines comprise a base on which a workpiece or workpieces to be cut are to be placed and clamped and a cutting head assembly in which a flexible endless bandsaw blade is trained around a pair of wheels or pulleys, one of which is power driven to drive the bandsaw blade. In the cutting head assembly, the bandsaw blade is slidably held and guided with its cutting edge faced perpendicularly downwardly by a pair of guide means at the cutting zone where cutting is performed so that it may cut into the workpiece to be cut. The cutting head assembly is so arranged as to be raised away from and lowered toward the base by a suitable means such as a hydraulic motor around a hinge pin or along one or more vertically disposed guide means. Thus, in each cutting cycle, the cutting head assembly is firstly raised and then lowered towards the base so as to enable the bandsaw blade being driven therein around the wheels to cut the workpiece which has been placed and clamped on the base.
In the horizontal bandsaw machines of the above described construction, it is desired that the bandsaw blade be adjustably fed into the workpiece to be cut at a higher or lower feeding speed and be adjustably driven at a higher or lower cutting or driven speed depending upon the nature and size of the workpiece. Stated more particularly, it is necessary that the bandsaw blade be fed at lower feeding and cutting speeds when cutting difficult-to-cut workpieces which are generally hard and tough. Also, it is necessary that the bandsaw blade be fed at higher feeding and cutting speeds when cutting normal easy-to-cut workpieces which are generally soft and brittle so as to obtain the desired cutting rate. Furthermore, it is necessary that the bandsaw blade be fed at a lower feeding speed to cut long cross-sectional lengths of the workpieces and be fed at a higher feeding speed to cut short cross-sectional lengths of the workpieces even though the workpieces may be the same nature or type of material.
Unless the feeding speed and the cutting speed of the bandsaw blade are correctly adjusted according to the nature and size of the workpieces to be cut, the cutting rate will be decreased and the life of the bandsaw blade will be shortened. The bandsaw blade will be often deflected or deviated from its normal cutting course when it is fed into the workpiece to be cut at an excessive feeding speed. Also, the bandsaw blade will become prematurely worn and be chipped when it is fed into the workpiece to be cut at an excessive cutting speed. On the other hand, the cutting rate will be decreased when the bandsaw blade is fed into the workpiece to be cut at much lower feeding or cutting speeds. Also, when the bandsaw blade is not fed at adequate feeding or cutting speeds when cutting difficult-to-cut workpieces which are generally hard and tough and mostly subject to work hardening, it will be unable to cut into the workpieces and will slide on the same only to scratch them without performing any cutting action with a result that a hard layer will be produced in kerves of the workpieces because of work hardening.
In order to perform cutting operations at a higher cutting rate with a longer life of the bandsaw blade, it is necessary to feed the bandsaw blade adjustably into the workpiece at adequate feeding and cutting speeds according to the nature and the cross-sectional length of the workpiece. In conventional bandsaw machines, however, it has been customary that the feeding and cutting speeds of the bandsaw blade are manually adjusted by the operator according to prescribed recommended cutting conditions and from his experience. Accordingly, it has been heretofore very troublesome and difficult to select and adjust the feeding and cutting speeds of the bandsaw blade for optimum cutting operations.